The present invention relates to ultrasound transducer barrier shields. In particular, shields for providing one or both of environmental and electrical protection for a transducer are provided.
To provide electromagnetic interference and environmental-chemical isolation, a thin shielding layer or film is positioned over ultrasound transducer elements, beneath the lens or window. For example, ultrasound transducers adapted to be inserted within the patient, such as a catheter-based transducer, are so shielded. Typically, a polyethyleneterephthalate (PET) film is bonded to a transducer stack with a castable elastomer, such as siloxane or urethane.
Transducers typically include an array of elements. Each transducer element is separated from other transducer elements by a kerf. When the shield layer is bonded, the kerfs are filled with the bonding adhesive. However, the directivity or acoustic roll off from each individual transducer element is not as good when the kerfs are filled with the liquid or cured solid adhesive as opposed to being filled with air or other gas.
To keep the kerfs filled with air, small amounts of adhesive may be used to bond the shield layer to the transducer stack. As a result, most of any given kerf is filled with air. However, uneven, partial fill, or a meniscus of the adhesive material is typically formed at the top portion of one or more of the kerfs. Different kerfs may have different amounts of partial fill; (i.e., irreproducible and variable degrees of kerf filling result). The element-to-element variability changes the acoustic directivity on a random basis. As a result, the acoustic directivity is neither as good nor as uniform as that provided by fully air- or gas-filled kerfs.